/*
 * Copyright 2001-2004 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package net.jforum.util.legacy.commons.fileupload;

import java.util.HashMap;
import java.util.Map;

/**
 * A simple parser intended to parse sequences of name/value pairs. Parameter
 * values are exptected to be enclosed in quotes if they contain unsafe
 * characters, such as '=' characters or separators. Parameter values are
 * optional and can be omitted.
 * 
 * <p>
 * <code>param1 = value; param2 = "anything goes; really"; param3</code>
 * </p>
 * 
 * @author <a href="mailto:oleg@ural.ru">Oleg Kalnichevski</a>
 */

public class ParameterParser {
    /**
     * String to be parsed.
     */
    private char[] chars = null;

    /**
     * Current position in the string.
     */
    private int pos = 0;

    /**
     * Maximum position in the string.
     */
    private int len = 0;

    /**
     * Start of a token.
     */
    private int i1 = 0;

    /**
     * End of a token.
     */
    private int i2 = 0;

    /**
     * Whether names stored in the map should be converted to lower case.
     */
    private boolean lowerCaseNames = false;

    /**
     * Default ParameterParser constructor.
     */
    public ParameterParser() {
	super();
    }

    /**
     * Are there any characters left to parse?
     * 
     * @return <tt>true</tt> if there are unparsed characters, <tt>false</tt>
     *         otherwise.
     */
    private boolean hasChar() {
	return this.pos < this.len;
    }

    /**
     * A helper method to process the parsed token. This method removes leading
     * and trailing blanks as well as enclosing quotation marks, when necessary.
     * 
     * @param quoted
     *            <tt>true</tt> if quotation marks are expected, <tt>false</tt>
     *            otherwise.
     * @return the token
     */
    private String getToken(boolean quoted) {
	// Trim leading white spaces
	while ((i1 < i2) && (Character.isWhitespace(chars[i1]))) {
	    i1++;
	}
	// Trim trailing white spaces
	while ((i2 > i1) && (Character.isWhitespace(chars[i2 - 1]))) {
	    i2--;
	}
	// Strip away quotation marks if necessary
	if (quoted) {
	    if (((i2 - i1) >= 2) && (chars[i1] == '"')
		    && (chars[i2 - 1] == '"')) {
		i1++;
		i2--;
	    }
	}
	String result = null;
	if (i2 > i1) {
	    result = new String(chars, i1, i2 - i1);
	}
	return result;
    }

    /**
     * Tests if the given character is present in the array of characters.
     * 
     * @param ch
     *            the character to test for presense in the array of characters
     * @param charray
     *            the array of characters to test against
     * 
     * @return <tt>true</tt> if the character is present in the array of
     *         characters, <tt>false</tt> otherwise.
     */
    private boolean isOneOf(char ch, final char[] charray) {
	boolean result = false;
	for (int i = 0; i < charray.length; i++) {
	    if (ch == charray[i]) {
		result = true;
		break;
	    }
	}
	return result;
    }

    /**
     * Parses out a token until any of the given terminators is encountered.
     * 
     * @param terminators
     *            the array of terminating characters. Any of these characters
     *            when encountered signify the end of the token
     * 
     * @return the token
     */
    private String parseToken(final char[] terminators) {
	char ch;
	i1 = pos;
	i2 = pos;
	while (hasChar()) {
	    ch = chars[pos];
	    if (isOneOf(ch, terminators)) {
		break;
	    }
	    i2++;
	    pos++;
	}
	return getToken(false);
    }

    /**
     * Parses out a token until any of the given terminators is encountered
     * outside the quotation marks.
     * 
     * @param terminators
     *            the array of terminating characters. Any of these characters
     *            when encountered outside the quotation marks signify the end
     *            of the token
     * 
     * @return the token
     */
    private String parseQuotedToken(final char[] terminators) {
	char ch;
	i1 = pos;
	i2 = pos;
	boolean quoted = false;
	boolean charEscaped = false;
	while (hasChar()) {
	    ch = chars[pos];
	    if (!quoted && isOneOf(ch, terminators)) {
		break;
	    }
	    if (!charEscaped && ch == '"') {
		quoted = !quoted;
	    }
	    charEscaped = (!charEscaped && ch == '\\');
	    i2++;
	    pos++;

	}
	return getToken(true);
    }

    /**
     * Returns <tt>true</tt> if parameter names are to be converted to lower
     * case when name/value pairs are parsed.
     * 
     * @return <tt>true</tt> if parameter names are to be converted to lower
     *         case when name/value pairs are parsed. Otherwise returns
     *         <tt>false</tt>
     */
    public boolean isLowerCaseNames() {
	return this.lowerCaseNames;
    }

    /**
     * Sets the flag if parameter names are to be converted to lower case when
     * name/value pairs are parsed.
     * 
     * @param b
     *            <tt>true</tt> if parameter names are to be converted to lower
     *            case when name/value pairs are parsed. <tt>false</tt>
     *            otherwise.
     */
    public void setLowerCaseNames(boolean b) {
	this.lowerCaseNames = b;
    }

    /**
     * Extracts a map of name/value pairs from the given string. Names are
     * expected to be unique.
     * 
     * @param str
     *            the string that contains a sequence of name/value pairs
     * @param separator
     *            the name/value pairs separator
     * 
     * @return a map of name/value pairs
     */
    public Map parse(final String str, char separator) {
	if (str == null) {
	    return new HashMap();
	}
	return parse(str.toCharArray(), separator);
    }

    /**
     * Extracts a map of name/value pairs from the given array of characters.
     * Names are expected to be unique.
     * 
     * @param chars
     *            the array of characters that contains a sequence of name/value
     *            pairs
     * @param separator
     *            the name/value pairs separator
     * 
     * @return a map of name/value pairs
     */
    public Map parse(final char[] chars, char separator) {
	if (chars == null) {
	    return new HashMap();
	}
	return parse(chars, 0, chars.length, separator);
    }

    /**
     * Extracts a map of name/value pairs from the given array of characters.
     * Names are expected to be unique.
     * 
     * @param chars
     *            the array of characters that contains a sequence of name/value
     *            pairs
     * @param offset
     *            - the initial offset.
     * @param length
     *            - the length.
     * @param separator
     *            the name/value pairs separator
     * 
     * @return a map of name/value pairs
     */
    public Map parse(final char[] chars, int offset, int length, char separator) {

	if (chars == null) {
	    return new HashMap();
	}
	HashMap params = new HashMap();
	this.chars = chars;
	this.pos = offset;
	this.len = length;

	String paramName = null;
	String paramValue = null;
	while (hasChar()) {
	    paramName = parseToken(new char[] { '=', separator });
	    paramValue = null;
	    if (hasChar() && (chars[pos] == '=')) {
		pos++; // skip '='
		paramValue = parseQuotedToken(new char[] { separator });
	    }
	    if (hasChar() && (chars[pos] == separator)) {
		pos++; // skip separator
	    }
	    if ((paramName != null) && (paramName.length() > 0)) {
		if (this.lowerCaseNames) {
		    paramName = paramName.toLowerCase();
		}
		params.put(paramName, paramValue);
	    }
	}
	return params;
    }
}
